Anticathode for discharge tubes



April 15, 1930. cs. HOLST ET AL 1,754,716

ANTICATHODE FOR DISCHARGE TUBES Filed March 8, 1926 I 2 z I 1 Patented Apr. 1 5,. i 1 930 UNITED STATES PATENT OFFICE e LtEs nons'r, Go'rrrnxnn BRUNO JONAS, AND ALBERT BOUWERS, or nmnnovmq,

NETHERLANDS, ASSIGNORS TO N. V. PHILIPS GLOEILAMPENFABRIEKEN, OF EIND- novntr. nn'rnnntnnns ANTICATHODE FOR nrscnnnen TUBES Application filedMar c h' 8, 1926, Serial No. 93,174, and in the Netherlands April 17, 1925.

This invention-relates to -an improvement in or modification ofthatdescribed in specification Nd 639,028 concerning an electrode for discharge tubes which has aglass wall sealed thereto, said electrode having a hollow 'chrome-ironportion to the edge of which the glass is sealed and-which shuts off the interior of the dischargeltubefrom the exterior. The present-invention has'for' its object to specially adapt such an electrode for the use as an anticathode in X-ray tubes. lit has namely been found that the fixation of the metal block destined for the emission of X-rays, to the chrome-ironfportion entails" some difliculties especiallyifthe metal block consists of tungsten which is frequently the case. These metals cannot be sealed together. In addition, the bad qconduction of heat of the chrome-iron adjacent to the metal block is a disadvantage whichonlycan be: avoided by rendering the chromeiron wall at this point.

very thin, "the: mechanical strength" of the anticathodegbemg, however, affected thereby.

According to the invention, these drawbacks are eliminated 'byproviding inside the hollow chrome-iron portion a metal or metal alloy of greatjheat conductivity which bears a metal block serving'to emit Ii-rays. As a metalsor metalalloy of great heat conductivity must be used a material which allows of being sealed both to the chrome-iron and to the metal blockis prepared. As such, for example copper, may be mentioned on condition that it be substantially pure. Commercial electrolytic red copper has proved to be very suitable for the purpose of the invention. The metal or metal-alloy of great heat conductivity should be separated wholly or almost wholly from the interior of the discharge tube owing to which the possibility that any ingredients detrimental to the tube and liberated from this material should enter into the tube, is diminished and-the material is prevented from being attacked by the discharge. This can be effected, according to an embodiment of the invention, by embedding the metal block serving for the emission of K-rays, in the metal of great heat conductivity and by enclosing the latter by an anthe accession of air.

portion having an inwardvaddition, offers the great advantage of allowng by a proper choice of the proportions of chrome and iron (for example 15-50% and 85%")070 respectively) to be very satisfactorily sealed to glass. in order to improve still more the dissipation of heat, a cooling device-which reaches outside the tube, may be'fixed to the metal'or metal alloy of great heat conductivity.

The present invention alsorelates to a process for the manufacture of the above described anticathodes for X-ray tubes. Ac-

cording to this process, a metal block destined for the emission of X-rays isarranged in a lit) chrome-iron vessel and then a metal or metal alloy of great heat conductivity is provided ,in the'said vessel whereupon the bottom of the vessel is removed to such an extent that the metal block is laid bare.

The process according to the present invention should preferably be carried out in such a manner that the metal or metal alloy of great heat conductivity after being introduced into the chrome-iron vessel, is melted while the airis shut out. This maybe efiected, for example, by placing the. chrome iron vessel during the melting of the metal or metal alloy provided'therein, in a vaccum space. In that case the metal or metal alloy may be heated for example, by placing the vessel in a high frequency magnetic field.

The shutting out of the airmay' also be efslag which protects the molten metal against drawing representing two embodiments of the invention. In this drawing Figure 1 represents an anticathode in which the surface of a metal block serves to emit X- rays in a direction parallel to the longitudinal directionof the chrome-iron vessel and Figure 2 represents an embodiment of the invention in which a metal block serves to emit X-rays in a direction erpendicular to the longitudinal direction 0 the chrome-iron vessel.

In Figure 1 the numeral 1 indicates a chrome iron vessel to which a glass wall 2 is sealed which forms part of the outer wall of an X-ray tube. Before the sealing of the vessel 1 to the lass portion 2 a metal block 3 which serves or the emission of X-rays is arranged in a recess of the bottom of the chrome-iron vessel 1. The block 3 may consist, for example, of tungsten. Thereupon some copper or other material of great heat conductivity is introduced into said vessel which then can be placed in a vacuum kettle in which it is heated beyond the melting point of the copper so that the copper forms a good conducting connection with the tungsten block 3. 'Ihereupon the vessel is slowly cooled; care must be taken that the cooling commences on the lower side of the vessel in order to prevent the production of flaws in the copper. The filling of copper indicated in the figure by 4 can then be turned out and be provided with a screw thread 5. The bottom of the vessel 1 is then removed, for example by grinding or by turning, to such an extent that the tungsten block is laid bare, the vessel obtaining thereby the shape indicated by the dotted line 6 in Figure 1. After the chrome-iron vessel has been sealed to the glass wall 2, a cooling tube 7 or a cooling rod may be screwed into the copper 4.

As observed already in the introduction, the heating of the copper or similar material of great heat conductivity need not always be carried out in a vacuum. Also substances may be introduced before or during the melting operation into the chrome-iron vessel, which substances form-on the copper a slag which shuts out the air. In this case the heating may be effected in any suitable manner for example with the aid of a gas burner or the like.

The embodiment of the invention shown in Figure 2, is substantially similar to that shown in Figure 1. In the two figures similar members are indicated by the same reference numerals. In this construction a chrome-iron block 8 having a sloping upper surface, is arranged in the vessel 1; this block serves as a bottom for the chrome-iron vessel and has a recess in which the tungsten block 3 is arranged. After the metal of great heat conductivity in the vessel 1 has been melted and cooled, the vessel 1 and the chrome-iron portion being filled with a metal of great eat conductivity, said metal bearing a metal block adapted to emit X-rays, the metal of great heat conductivity being shut oft from the interior of a discharge tube when used I therein partly by said chrome-iron portion and partly by said metal block.

2. An electrode adapted to be used as an anticathode in X-ray tubes, said electrode having a hollow chrome-iron portion to the edge of which a glass wall can be sealed, said portion having an inwardly extending flange and being filled with a metal of great heat conductivity, which metal bears a metal block adapted to emit X-rays, said metal of great heat conductivity being shut ofi" from the interior of a discharge tube when used therein partly by said chrome-iron portion and partly by said metal block.

3. A process for the manufacture of an anticathode for X-ray tubes which consists in placing a metal block adapted to emit X- rays in the bottom of a hollow chrome-iron vessel, to the edge of which a glass wall can be sealed, introducing a metal of great heat conductivity into said vessel and removing thereupon part of the bottom of the vessel to such an extent that the metal block is laid bare.

i. A process for the manufacture of an anticathode for X-ray tubes according to claim 3 in which the bottom of the vessel is removed to such an extent that the metal block is laid bare while the metal of great heat conductivity is shut oil wholly from the interior of a discharge tube when used therein.

5. A process for the manufacture of an anticathode for X-ray tubes according to claim 3, in which the metal of great heat conductivity is melted after being introduced into the chrome-iron vessel while shutting out the air.

In testimony whereof we afiix our signatures, at the city of Eindhoven, this 11th day of February. A. D. 1926.

GILLES HOLST. GOTTFRIED BRUNO JONAS. ALBERT BOUWERS.

(sea!) I CERTIFICATE OF CORRECTION. Patent No. 1,754,716. I Granted April 15,1930; to

GILLES HOLST ET AL.

It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 1, line 32, 'for the word "prepared" read "preferred"; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office. I

Signed and sealed this 13th'day of May, A. D. 1930.

M. J. Moore, Acting Commissioner of Patents. 

